1. Field of the Invention
This invention relates to an apparatus for examining for the presence or absence of ophthalmic diseases in a patient's eye, and more particularly to an apparatus for detecting ophthalmic diseases in which laser light is radiated via an optical system at one spot in the camera oculi of the patient's eye, particularly in the anterior chamber thereof, and the laser light scattered therefrom is analyzed to measure the protein concentration for ophthalmic disease detection in the camera oculi.
2. Description of the Prior Art
The camera oculi is comprised of the camera oculi anterior (anterior chamber) and the camera oculi posterior (posterior chamber). The camera oculi anterior is defined by a space surrounded by the rear surface of the cornea, a part of the ciliary body, the iris, and the front surface of the crystalline lens, while the camera oculi posterior is defined by a space surrounded by the rear surface of the iris, the inner surface of the ciliary body, and the front surface of the crystalline lens. The camera oculi is filled with transparent humor aqueous, which has chemical and physical characteristics that are different from those of lymphatic liquid and has a close relation with the metabolism of the cornea or crystalline lens. The humor aqueous contains proteins the increase of which causes turbidity in the camera oculi when it becomes inflamed.
In this respect, the measurement of protein concentration in the camera oculi of the patient's eye is of great importance in determining whether the camera oculi is inflamed, that is, whether a blood-aqueous barrier functions normally or not.
To measure the protein concentration in the camera oculi, a slit lamp microscope is very often used to determine the turbidity by grading via the naked eye. This is, however, disadvantageous because the judgment depends upon the person who performs the measurement.
On the other hand, a photographic measuring method has been developed to make a quantitative measurement of the protein concentration. This method is, however, highly complicated to analyze, and is thus very difficult to apply in a clinical examination.
To overcome this problem, an apparatus for detecting ophthalmic diseases has been proposed which includes means for focusing a laser beam at a selected spot in the camera oculi of an eye. In the apparatus, the light scattered from the eye is photoelectrically detected and converted into an electrical signal which is subsequently used to determine the protein concentration essential to ophthalmic disease detection in the camera oculi of the patient's eye. See, for example, Japanese Patent Laying-open No. 120834/87.
Such use of a laser beam to focus on a selected spot in the camera oculi of an eye for ophthalmic measurement by detecting light scattered from the eye conventionally has been accompanied by such problems as an increased intensity of the laser beam imposing major discomfort on the patient as well as a high risk. If, in order to avoid this, a small-output laser light source is employed, the intensity of the laser beam impinging on the camera oculi is reduced, and as a consequence it is necessary to raise the sensitivity of the light detection system, raising the cost of the overall apparatus.